This document outlines Pedro's experience running engineering teams and details the evolution of Unicorn's on-call program over time from the Stone Age to the Iron Age. It began with everyone being on-call and no formal program. Over time, they introduced dedicated on-call teams, defined compensation and procedures, improved alarm handling, and focused on reducing burnout. The final section reflects on lessons learned like tuning alarms, avoiding rushed decisions, and keeping stakeholders informed during incidents.